An electro-photographic type image forming apparatus such as a laser printer and an LED printer is well known in the art. A developing cartridge is used for the image forming apparatus. The developing cartridge includes a developing roller for supplying toner. The conventional image forming apparatuses are described in the prior art. An image forming apparatus described in the prior art includes a drawer unit. The drawer unit includes a photosensitive drum. The developing cartridge is attachable to the drawer unit. When the developing cartridge is attached to the drawer unit, the developing roller contacts the photosensitive drum.
A developing cartridge disclosed in another prior art is attachable to a drum cartridge. The drum cartridge includes a photosensitive drum. When the developing cartridge is attached to the drum cartridge, the developing roller contacts the photosensitive drum. Then, the drum cartridge to which the developing cartridge has been attached is attached to a main casing of an image forming apparatus.